In this research, pitting corrosion behavior of 2205 duplex stainless steel in acetic acid solution was investigated. Using cyclic polarization tests, effects of different concentrations 0.01, 0.1, 0.2 and 0.5M sodium bromide and sodium chloride on the pitting corrosion of 2205 stainless steel was studied. In addition, effects of temperature and nitrite inhibitor were also investigated. Pitting potential was found to be decreased by increasing the temperature and bromide ion concentration. In the presence of chloride ions, pitting corrosion was not observed at room temperature. Critical Pitting Temperature (CPT) and Critical Protection Temperature (CPrT) in the chloride solution was estimated to be below 45°C. The pitted surfaces were iected by SEM after anodic polarization readings and showed that pits initiate in the austenite phase. The results of Electrochemical Impedance Spectroscopy (EIS) and mott-schottky tests showed that, by increasing the temperature, thickness of passive film is decreased and donor density of passive film is increased. Pitting potential was decreased by increasing the nitrite concentration, and proper inhibition efficiency was achieved by the presence of 500 to 1000ppm of anion. EIS measurements showed that the charge transfer resistance increases and double layer capacitance decreases with increase in the nitrite concentration. Cyclic potentiodynamic polarization readings showed that the nitrite anions act anodically. Key Words Duplex stainless steel, Pitting corrosion, Sodium bromide. Sodium chloride, Sodium nitrite, Corrosion inhibition
